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13-06-2010, 10:01
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#1
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Registered User
Join Date: Jul 2005
Posts: 318
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Oil Senders & Teflon Tape
Ok, I just rebuilt a new gauge panel and replaced all my senders for Oil Pressure and Oil Low Pressure Alarm. They are both on a bronze "T" from the lower block. Turns out they are leaking around the threads.
Can I use teflon tape on the oil sender threads? This is an attempt to stop the leaks.
I know you can't use it on the Water Temp because it blocks the sender from self grounding. Is it the same for a normally on pressure switch like an oil sender?
I know, I know...................go read the damn instructions.
Well they're on the boat and I'm at home on a Sunday morning.
I appreciate any help.
__________________
It's kind of like tearing up $100 bills while standing in a cold shower.
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13-06-2010, 10:11
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#2
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Moderator Emeritus

Join Date: Sep 2007
Location: Eastern Tennessee
Boat: Research vessel for a university, retired now.
Posts: 10,406
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Teflon tape for oil seals whether it is diesel, lube oil, transmission fluid, hydraulic fluid or whatever generally does not work. I use #3 Aviation grade Permatex for oil related seals.
Description: Non-hardening liquid gasket sealant/dressing/coating is a thin, brushable dressing or sealer for close-fitting parts. Suitable for continuous temperatures to 400˚F (204˚C). Resistant to antifreeze, aviation fuels, high-detergent oils and lubricants. Conforms to MIL-S-45180 D. Suggested applications: Gasket coating or sealing close-fitting machined parts.
The sender will ground just fine.
__________________
David
Life begins where land ends.
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13-06-2010, 10:17
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#3
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Senior Cruiser

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 47,078
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Quote:
Originally Posted by Maddog
... I know you can't use it on the Water Temp because it blocks the sender from self grounding. Is it the same for a normally on pressure switch like an oil sender?
I know, I know...................go read the damn instructions.
Well they're on the boat and I'm at home on a Sunday morning.
I appreciate any help.
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Yes, typical oil senders (1 wire) are also body grounded, so you cannot use Teflon.
Instead use blue Permatex (thanks David) or LocTite.
Yes, do read the instructions.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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13-06-2010, 12:24
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#4
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Eternal Member
Join Date: Aug 2006
Location: North of Baltimore
Boat: Ericson 27 & 18' Herrmann Catboat
Posts: 3,798
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Areyou sure the pipe thrreads are the same?
Teflon is NOT to be used for oil or diesel
Silicone is a no-no
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13-06-2010, 12:46
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#5
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Senior Cruiser

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 47,078
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Quote:
Originally Posted by Maddog
Ok, I just rebuilt a new gauge panel and replaced all my senders for Oil Pressure and Oil Low Pressure Alarm. They are both on a bronze "T" from the lower block. Turns out they are leaking around the threads...
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Quote:
Originally Posted by Chief Engineer
Are you sure the pipe thrreads are the same?
Teflon is NOT to be used for oil or diesel
Silicone is a no-no
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Sender “T/Y” adapters are very prone to leaking & breakage.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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13-06-2010, 14:46
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#6
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Registered User
Join Date: Jul 2005
Posts: 318
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Thanks guys - Permatex it is.
__________________
It's kind of like tearing up $100 bills while standing in a cold shower.
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15-07-2010, 23:16
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#7
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Registered User
Join Date: Jul 2005
Posts: 318
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Just got back from the boat and the permatex did the trick.
Thanks
__________________
It's kind of like tearing up $100 bills while standing in a cold shower.
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16-07-2010, 05:04
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#8
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Registered User
Join Date: Feb 2008
Location: North Charleston, SC
Boat: Camano Troll
Posts: 5,069
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Quote:
Originally Posted by Maddog
Can I use teflon tape on the oil sender threads? This is an attempt to stop the leaks.
I know you can't use it on the Water Temp because it blocks the sender from self grounding. Is it the same for a normally on pressure switch like an oil sender?
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It's been said, but teflon tape will insulate the sender from the block and break the electrical circuit.
It has nothing to do with diesel, oil, or whatever, the sender must make electrical contact with the block to complete the circuit.
__________________
Ron
HIGH COTTON
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16-07-2010, 05:59
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#9
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Moderator Emeritus

Join Date: Sep 2007
Location: Eastern Tennessee
Boat: Research vessel for a university, retired now.
Posts: 10,406
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This is true, many engine block sensors use their threads as a ground.
It is also very true that oil can leak slowly past Teflon tape wound around threads. I have seen it from somebody who did this with a diesel fuel line.
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David
Life begins where land ends.
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16-07-2010, 07:01
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#10
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Registered User
Join Date: Feb 2008
Location: North Charleston, SC
Boat: Camano Troll
Posts: 5,069
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Quote:
Originally Posted by David M
This is true, many engine block sensors use their threads as a ground..
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Any thing with only one wire attached is using the engine, fuel tank, transmission, etc. as a ground.
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Ron
HIGH COTTON
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16-07-2010, 07:04
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#11
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Senior Cruiser

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 47,078
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Quote:
Originally Posted by rwidman
Any thing with only one wire attached is using the engine, fuel tank, transmission, etc. as a ground.
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Indeed.
AND:
Teflon tape is to be used only on fittings that seal on the threads, ie: Tapered Jointing threads such as type NPT or BSPT/Whitworth.
Do NOT use tape on Fastening threaded fittings, that seal at the tip or at the bolt head. So banjo, AN/jic/37 degree, bubble flare, inverted flare, 45 degree flare and a host of others are designed to seal without tape.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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16-07-2010, 11:15
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#12
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Registered User
Join Date: Feb 2008
Location: North Charleston, SC
Boat: Camano Troll
Posts: 5,069
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Quote:
Originally Posted by rwidman
Any thing with only one wire attached is using the engine, fuel tank, transmission, etc. as a ground.
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I'll go ahead and add that any plumbing that's bonded such as a tailpiece on a seacock should be sealed with pipe dope, not teflon tape.
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Ron
HIGH COTTON
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